Martins Dorival, McKay Geoffrey A, English Ann M, Nguyen Dao
Meakins-Christie Laboratories, Research Institute of the McGill University Health Centre, Montreal, QC, Canada.
Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada.
Front Microbiol. 2020 Sep 25;11:576708. doi: 10.3389/fmicb.2020.576708. eCollection 2020.
Stressors and environmental cues shape the physiological state of bacteria, and thus how they subsequently respond to antibiotic toxicity. To understand how superoxide stress can modulate survival to bactericidal antibiotics, we examined the effect of intracellular superoxide generators, paraquat and menadione, on stationary-phase antibiotic tolerance of the opportunistic pathogen, . We tested how pre-challenge with sublethal paraquat and menadione alters the tolerance to ofloxacin and meropenem in wild-type and mutants lacking superoxide dismutase (SOD) activity (), the paraquat responsive regulator , (p)ppGpp signaling ( mutant), or the alternative sigma factor . We confirmed that loss of SOD activity impairs ofloxacin and meropenem tolerance in stationary phase cells, and found that sublethal superoxide generators induce drug tolerance by stimulating SOD activity. This response is rapid, requires protein synthesis, and is RpoS-dependent but does not require (p)ppGpp signaling nor SoxR. We further showed that pre-challenge with sublethal paraquat induces a SOD-dependent reduction in cell-envelope permeability and ofloxacin penetration. Our results highlight a novel mechanism of hormetic protection by superoxide generators, which may have important implications for stress-induced antibiotic tolerance in cells.
应激源和环境线索塑造了细菌的生理状态，进而影响它们随后对抗生素毒性的反应。为了解超氧化物应激如何调节对杀菌性抗生素的耐受性，我们研究了细胞内超氧化物生成剂百草枯和甲萘醌对机会致病菌静止期抗生素耐受性的影响。我们测试了用亚致死剂量的百草枯和甲萘醌预先刺激如何改变野生型以及缺乏超氧化物歧化酶（SOD）活性的突变体（）、百草枯反应调节因子、（p）ppGpp信号传导（突变体）或替代西格玛因子对氧氟沙星和美罗培南的耐受性。我们证实，SOD活性的丧失会损害静止期细胞对氧氟沙星和美罗培南的耐受性，并发现亚致死性超氧化物生成剂通过刺激SOD活性诱导药物耐受性。这种反应迅速，需要蛋白质合成，且依赖RpoS，但不需要（p）ppGpp信号传导也不需要SoxR。我们进一步表明，用亚致死剂量的百草枯预先刺激会导致细胞包膜通透性和氧氟沙星渗透性的SOD依赖性降低。我们的结果突出了超氧化物生成剂的一种新型应激保护机制，这可能对细胞中应激诱导的抗生素耐受性具有重要意义。
